This invention relates to a solvent-free organosiloxane composition containing liquid organopolysiloxane as a major component, and uses thereof. More particularly, it relates to a solvent-free organosiloxane composition which can form, when in contact with water or heat of up to 300.degree. C., a polymer having polysiloxane bonds as a main chain and having a good flexibility, and which can be used for forming a film, fibers, a coating material, a binder, a composite structure or a building material and uses of the composition.
Solvents have so far been important for preparing coating compositions, generally accounting for 45 to 50% of such paint compositions. More than 50 kinds of solvents are illustrated as major solvents. In particular, organic solvents are important and indispensable for dissolving or dispersing film-forming materials to impart a proper fluidity, coating properties and film-forming properties. Thus, organic solvents have so far been inevitable for producing coating compositions.
However, organic solvents can be described as dangerous objects due to their high combustibility and capability to induce various troubles (e.g., anesthesia, troubles of the central nervous system and the autonomic nervous system, troubles of liver and kidney, and inflammation of skin or eye), thus requiring control and caution in handling.
The environment of the earth cannot afford the use of such combustible, dangerous organic solvents which induce human troubles in daily commodities. Thus, it has been eagerly desired to develop solvent-free coating compositions. Although aqueous emulsion coating compositions and powder coating compositions have been developed as solvent-free coating compositions, these coating compositions have failed to have sufficient coating properties.
In general, varnishes, coating compositions, adhesives, fibers, and the like are mainly based on organic resins. Recent living environmental regulations have required incombustible or fire retardant, pollution-free materials in many fields. Under such situations, the use of organic solvents which are dangerous and can cause environmental pollution has been brought into question. Hence, pollution-free materials involving no such problems have eagerly been desired.
In order to meet the requirement, siloxane compounds which have Si--O bonds resistant against heat or light and which have good weatherability and high heat resistance have widely been investigated, part of the investigation results having been put into practice. Typical examples of the results and remaining problems are described hereinafter mainly referring to coating compositions and coating materials.
As a popular example of applying organosiloxanes to coating compositions, there are illustrated zinc-rich coating compositions developed in World War II. These coating composition comprise a hydrolyzed product of tetraethoxysilane diluted with about the same amount of isopropyl alcohol and about two-fold amount of zinc powder. This type of compositions is being widely used as anti-corrosive paints capable of forming a coating film at ordinary temperature.
There have been developed coating compositions prepared by diluting, with an organic solvent, polymers of organosiloxane or modified organosiloxane or copolymers thereof with various organic compounds, together with or without other organic resins. Most of the conventionally developed techniques are based on the above-described compositions. For example, a technique of preparing a modified tetraalkoxysilane as a filming agent in the presence of the same or more amount of a solvent, and applying the composition to an object, followed by air-drying or hot-air drying to form a heat-resistnt, anti-corrosive coat is disclosed in, for example, Japanese Examined Patent Publication No. 63-28942, and a technique of diluting an organosiloxane with an organic solvent and forming a film using the composition at an ordinary temperature or uder heating is disclosed in, for example, Japanese Examined Patent Publication No. 63-58191.
There have been many examples of merely combining organic compounds (organic resins) and organosiloxanes to prepare coating materials or the like. Most of them require heating upon film formation. Typical example thereof is described in Japanese Examined Patent Publication No. 55-41274, etc. wherein tetraethoxysilane and methyltriethoxysilane are mixed with polyvinyl butyral butylated methylolmelamine, and an object coated by the mixture is heated to 130.degree. C. to form a coat.
Many studies have been made on utilization of organosiloxane as filming agent of heat-resistant coat. Japanese Examined Patent Publication No. 63-35183 discloses one typical example thereof wherein a coating composition prepared by adding a slight amount of an aluminum chelate compound to 50-80% by weight of a heat-resistant inorganic material (e.g., aluminum phosphate, zinc molybdate, calcium carbonate, zinc silicate powder, etc.), and adding thereto 20 to 50% by weight of a modified silicone resin is applied to an object, followed by baking at 180.degree. C. to form a heat-resistant coat.
As an example of utilizing pure organosiloxane, there is illustrated a technique of preparing a durable, stainproof transparent film composed of organosiloxane, an organotin compound and a volatile dimethylpolysiloxane (Japanese Unexamined Patent Publication No. 3-68676).
A technique of using a keto-enol tautomer compound for stabilizing a curing catalyst of a metal-containing organic compound in the polymer-forming organosiloxane has also been disclosed. For example, Japanese Examined Patent Application No. 48-17859 discloses this technique with respect to a mixed system of a linear copolymer having carboxyl groups within the molecule, an aluminum alcoholate complex compound, and a solvent. As a similar technique, Japanese Unexamined Patent Application No. 1-129066 discloses to use a keto-enol tautomer compound together with a curing agent of chelate compound in a mixed system of a resin having isocyanato groups, hydroxyl groups, epoxy groups, carboxyl groups and/or amino groups partly reacted with alkoxysilane group or hydroxysilane group, an epoxy resin and an organic solvent.
Techniques of curing a one-pack type organosiloxane composition at an ordinary temperature are disclosed in U.S. Pat. Nos. 3,294,739, 3,647,917 and 4,111,890. However, these patents do not disclose a technique of limiting the content of metals such as silicon in the composition to a particular range to thereby solve the problem of inorganic hardness and fragility with respect to a cured product containing the metals in high content, impart good flexibility to the cured product, and improve adhesiveness to a substrate.
In addition, it has not been disclosed, either, to apply the cured product with improved flexibility not only to a coating composition but to a building material, a sheet, fibers or the like.
The inventors have formerly made an invention relating to a solvent-free organosiloxane composition which, when subjected to specific conditions, can be cured at an ordinary temperature or under heating to provide a product such as a coating material and a binder, and have filed the invention as Japase Patent Application Nos. 4-180127 and 4-36273.
This formerly filed invention is characterized in that the content of the total metal elements in the solvent-free organosiloxane composition is 40% by weight or more in terms of MO.sub.y/2. As a result of further investigations, the inventors have found that an organosiloxane liquid composition of less than 40% by weight in the content of the total metal elements can solve the problem of the inorganic hardness and fragility with respect to the cured product containing metal elements in high total content, can impart good flexibility to the product, and can improve adhesiveness to a substrate or the like, thus having completed the present invention.
In this specification, a siloxane cured product containing, as a main chain, a polysiloxane bond formed by bringing the solvent-free organosiloxane liquid composition of the present invention into contact with water or heat of up to 300.degree. C. is in some cases abbreviated as "siloxane polymer composition".
In addition, the contents of metal elements such as aluminum, boron, silicon, titanium, zirconium, zinc and cobalt are in some cases presented in terms of "MO.sub.y/2 weight %".
The term "adhesively accompanying property" as used herein in the present specification means the property that, when the polymer material is applied to a substrate (e.g., a metal plate such as a steel plate; a cement product such as an asbestos plate; a wood; etc.) and is then exposed to natural environment conditions for a long time, the polymer can expand or contract to the expansion or contraction of the substrate, thus the adhesion therebetween being maintained.
Several words are defined as follows and will be described in detail in the specific description of the invention to be described hereinafter.
The term "siloxane polymer composition" is a general term for cured siloxane products constituting a shaped polymer composition, an adhesive polymer composition, a composite structure, a composite sheet and a building material.
The term "shaped polymer composition" means a shape-retaining polymer composition which is composed of a cured product of the organosiloxane liquid composition of the present invention alon and is shaped in a particular form such as a film, a thin plate, a sheet, fibers, a string, a mass, a sphere, a rectangular member, etc.
The term "adhesive polymer composition means a polymer composition which forms a coating film or a binder adhering to the surface of various substrates and can be used as, for example, a coating composition, a varnish, an undercoating composition, a protective coating material having some thickness, an adhesive, a binder, a joint mixture, an agent for binding aggregates, a cementing material, and an anchor-fixing material.
The term "composite structure" means a structure wherein a cured product of the organosiloxane liquid composition of the present invention functions to unify a reinforcing material in a various shape such as a honeycomb, a massive structure, a plate, a net, fibers, a cloth, etc, aggregates, moldings, or a shaped product.
The term "composite sheet" means a sheet wherein a cured product of the organosiloxane liquid composition of the present invention unifies with a base material in a form of a sheet, net, cloth or texture.
The term "building material" means a building material wherein a cured product of the organosiloxane liquid composition of the present invention is coated on the surface of a building material base such as a metal product (e.g., iron-made product), a concrete product, a ceramic or clay product, a product of a natural material such as wood or bamboo, a synthetic product, etc.
As has been seen with the above-described prior art, the application of the organopolysiloxane as a coating component has mostly begun with auxiliary addition to an organic compound-based coating composition containing an organic polymer or an organic resin having a main chain of C--C bonds and being excellent in filming properties, dilution properties with a solvent and drying properties after being coated for the purpose of improving the coating composition.
Hence, these conventional coating compositions inevitably contain the dangerous, trouble-causing organic solvents, and there have been seen no positive attempts to produce and commercialize solvent-free coating compositions mainly using organosiloxane, and an incombustible or fire retardant siloxane polymer composition such as a shaped polymer composition in a form of film or fiber and an adhesive polymer composition such as a coating material or an adhesive.
On the other hand, development of products having enhanced incombustibility or fire retardant properties and enhanced hardness due to high content of inorganic ingredients such as silicon. However, there have been completed no techniques of imparting good flexibility to a siloxane polymer composition and improving adhesively accompanying properties to a substrate by limiting the content of metal elements such as silicon.
The inventor has given attention to the following fundamental problems which conventional films, fibers, coating compositions, coating materials, binders, structures, sheets, building materials, etc. utilizing the above-described prior art polymers and to the fact that there have been no techniques which take into consideration protection of the environment of the earth and saving of energy and labor.
1) In the case of using an organic compound having C--C bonds as the main chain: PA1 2) In the case of using a silicon compound having incombustible S--O bonds as the main chain: PA1 (1) A liquid composition constituted by a particular liquid organopolysiloxane, a cross-linking agent of organometallic compound and a curing catalyst can form a liquid coating composition without any solvent; PA1 (2) Particularly, when the content of the total metal elements of the organosiloxane liquid composition is controlled within the range of from 25% by weight to less than 40% by weight, there can be formed a siloxane polymer composition which has sufficient heat resistance with no fragility and which exhibits good adhesively accompanying properties to the substrate for a long time. PA1 (3) When a metal-containing organic compound is allowed to be present in the aforesaid particular organosiloxane liquid composition, it can form the above-described effective cured polymer product when brought into contact with heat or water due to moisture curing mechanism; and PA1 (4) When the above-described organosiloxane liquid composition contains B--O bonds, Ti--O bonds, Zr--O bonds, etc., the polymer having a main chain comprised of --Si--O-- bonds can exhibit highly functional polymer performance that cannot be obtained by the prior art. PA1 (1) A shaped polymer composition in a form of a film, thin sheet, fibers, strand, mass, sphere, square bar or other specific form, formed without other materials. PA1 (2) An adhesive polymer composition to be applied to the surface or interior of various substrates such as a coating or varnish, a protective coating having some thickness, an adhesive, a binder, a joint mixture, amassing or unifying agent for various aggregates, a cementing material, and an anchor-fixing material. PA1 (3) A composite structure unified with a reinforcing material with a form of honeycomb, mass, plate, net, fiber or cloth or with aggregates, moldings or structural products. PA1 (4) A composite sheet unified with a sheet base with a form of film, net, cloth or texture. PA1 (5) A building material formed by applying the siloxane composition to the surface of a building material base such as a metal product (e.g., an iron-made product), a concrete product, a ceramic or clay product, an enamel product, a prduct of a natural material such as wood or bamboo or a synthetic product thereof.
(a) use of an organic solvent which is dangerous and harmful is inevitable; PA2 (b) the composition is quite susceptible to oxidation by heat or fire; PA2 (c) a poisonous and harmful gas is produced upon combustion; PA2 (d) the composition provides quite poor weatherability. PA2 (a) the composition provides poor flexibility; PA2 (b) the composition provides poor alkali resistance due to its high reactivity with an alkali metal element; PA2 (c) cured products containing Si--O-- bonds formed due to hydraulic property contain many pores, thus the products lack water impermeability; PA2 (d) the composition cannot be applied to a material composed of inorganic Si--O bonds since organic materials have no adhesion property to the inorganic surface.
In addition to the above-described problems, the inventor has given attention to the fact that, in the formerly made invention (Japanese Patent Application Nos. 4-180127 and 4-36273), only insufficient care was taken with respect to the adhesively expanding or contracting property to the expansion or contraction of the substrate.